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Ring opening polymerization (ROP) of ε-caprolactone (CL) was carried out by bulk polymerization technique using stannous octoate (SO) as a catalyst and in the presence of macro or molecular initiator for 5 h under inert atmosphere with mild stirring. The % yield of poly(ε-caprolactone) (PCL) obtained was calculated and compared based on the chemical structure of macro and molecular initiators. Various analytical techniques such as FT-IR, 1H-NMR, XPS, GPC, DSC, TGA, SEM and WCA were used to characterize the PCL. The FT-IR spectrum showed the C=O stretching around ∼1725 cm−1. The aromatic proton signal of isoeugenol (IE) initiator appeared at 7–8 ppm in the proton NMR spectrum. The experimental results obtained were compared with the literature values.

The ring opening polymerization (ROP) kinetics of L-lactide was studied in bulk at 150, 160, and 180 °C using stannous octoate [Sn(Oct)2] catalyst and 1-pyrene butanol co-catalyst. The effect of di...

This study determined that both triethylamine hydrochloride (TEA·HCl) and TEA can catalyze the melt polymerization of several carbonate monomers at 65–150 °C. TEA·HCl's catalytic activity is especially noteworthy because it is a common by-product in the synthesis of carbonate monomers. Melt polymerizations of trimethylene carbonate (TMC) catalyzed with TEA achieved monomer conversions ranging from 97% in 6 h at 85 °C to 98% in 1 h at 110 °C and those catalyzed with TEA·HCl ranged from 98% in 12 h at 85 °C to 98% in 1 h at 110 °C using a monomer : initiator : catalyst ratio of 50 : 1 : 0.1. By contrast, TMC polymerizations conducted with stannous octoate, a widely used catalyst, required at least twice as long to achieve the same monomer conversion (24 h at 85 °C and 2.5 h at 110 °C). Catalyst-free polymerization was also observed at temperatures and timespans below those previously reported, with 99% conversion in 32 h at 85 °C and 99% conversion in 2.5 h at 110 °C.

A porous Sn@C nanocomposite was prepared via a facile hydrothermal method combined with a simple post-calcination process, using stannous octoate as the Sn source and glucose as the C source. The as-prepared Sn@C nanocomposite exhibited excellent electrochemical behavior with a high reversible capacity, long cycle life and good rate capability when used as an anode material for lithium ion batteries.

A novel plasticizer (lacti-glyceride) synthesized by esterification of glycerol with l-lactic acid was developed for thermal processing of PVA/PLA blend. Meanwhile, the stannous octoate (Sn(Oct)2) was used as the catalyst for the transesterification reaction of PVA, PLA, and the plasticizer. The results showed that the PVA/PLA blends plasticized with lacti-glyceride have improved thermal processability and mechanical properties compared to those plasticized with glycerol, because the lacti-glyceride may act not only as a plasticizer but also as a compatibilizer for PVA and PLA. SEM images indicated that PVA/PLA blends catalyzed with Sn(Oct)2 had better compatibility than those without catalyst. Water contact angle measurements showed that the PVA/PLA blends plasticized with lacti-glyceride have much more hydrophobic surfaces than those blends plasticized with glycerol. The blends will find wider applications than PVA.

A comprehensive mathematical model was developed based on a detailed kinetic mechanism to predict the dynamic evolution of monomer conversion and molecular weight averages. The predictive capabilities of the mathematical model are demonstrated by a direct comparison of model predictions with literature and new experimental data on monomer conversion as well as number and weight average molecular-weight of PLLA. The effects of monomer to initiator molar ratio and polymerization temperature on the polymerization rate and average molecular weight properties of polylactide were experimentally determined and compared with model predictions. For this reason, high molecular weight polylactides were synthesized in melt via the ring-opening polymerization of L,L-lactide, in the presence of stannous octoate.

The foaming reaction so that all water-gel reaction and foaming reaction to reach equilibrium, the excellent thermal insulation material was prepared by the regulation of the catalyst, a nucleating agent and an isocyanate. By experiment we know that the amount of stannous octoate catalyst 6%, 4% of the amount of nucleating agent CaCO3, and the case of 100% of the amount of isocyanate, the density of the foam material and the mechanical properties of the insulation material to achieve the best value.

The general purpose of polyurethane chemical recycling is to recover constituent polyol. Among the suitable processes, glycolysis, and specially glycolysis in two-phases is the one that allows recovering the polyol with the highest quality in comparison to single-phase processes. Recently stannous octoate has been stated as the catalyst that provides the fastest decomposition rate and the one that allows obtaining a recovered polyol with similar characteristics to fresh polyol. In this work a study of the main reaction parameters has been carried out. Optimal catalyst concentration, ratio of glycolysis agent to treated PU foam and optimal reaction temperature have been determined.

Random copolymers of trimethylene car- bonate (TMC) and e-caprolactone (CL) have been synthe- sized by ring-opening polymerization of TMC and CL in the presence of stannous octoate. The effects of feeding dose, reaction temperature and polymerization time, and effect of catalyst content on the copolymerization were investigated. The results showed that the composition of the copolymers was in good agreement with the feeding dose, and the molecular weight of the copolymers decreased firstly with increasing CL content and then increased. The decrease in the reaction temperature, poly- merization time and catalyst content would increase the molecular weight of the copolymers. Furthermore, the feeding dose affected the thermal and mechanical proper- ties of the copolymer largely, and the possessing different properties of random copolymers could be obtained by adjusting the copolymer compositions. This work could optimize the polymerization conditions to achieve the copolymers with controlled properties for implant applica- tions. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: 3714- 3720, 2012

A family of poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL) were synthesized in high yields by the ring-opening polymerization of monomethoxy-terminated poly(ethylene glycol) (mPEG) with ε-caprolactone in the presence of stannous octoate (Sn(Oct)2). Their crystallization behaviors were studied by DSC, XRD. The results illustrated that crystallization behaviors of the copolymers depended on the copolymer composition and the relative length of each block in copolymers. The melting peak of PCL block appeared gradually in the XRD patterns and DSC curves in copolymers, with increasing of the length of PCL blocks.

12 páginas., Short 2-hydroxyethylmethacrylate (HEMA)-oligocaprolactone macromonomers were synthesized at different temperatures from 100° to 190°C by bulk ring opening polymerization using HEMA as initiator and stannous octoate as catalyst. The crude products were analysed by MALDI-TOF and NMR and the influence of the temperature on the reaction was studied. In addition to transesterification (found at temperatures of 130°C and higher), other secondary reactions involving HEMA breakdown were also identified at these temperatures. In these processes, difunctional acrylic compounds may be formed.

A series of undyed 90/10 (mol %) poly(p-dioxanone-co-glycolide) block copolymers were synthesized by ring-opening polymerization, with stannous octoate as a catalyst, utilizing various ratios of mo...

The thermal decomposition rate constant kd of 2,2′-azobis(isobutyronitrile) (AIBN) in ethyl acetate was determined at 60 °C in the presence of various amounts of stannous octoate (SnOc2). The kd values were found to be dependent on the concentration of SnOc2 in the solution. This dependence is not a linear function of the concentration because kd goes through a maximum when [SnOc2]/[AIBN] = 1. These features were explained by assuming the formation of a 1:1 cyclic complex between the nitrile groups of AIBN and the tin atom of SnOc2. This complex induces steric constraints in the azo bond of AIBN, thus increasing its rate of decomposition. © 2000 Society of Chemical Industry

Linear and star-shaped copolymers of trimethylene carbonat/epsilon-caprolactone were synthesized using different polyol initiators and catalysts. Unexpectedly, when dipentaerythritol was used as an initiator cross-linked rubbers were obtained, that swell in chlorofonn. This network formation can be understood by 'in situ' generation of cross-linker molecules from trimethylene carbonate and initiator tor. SEC analysis showed that with D-sorbitol star-shaped copolymers are synthesized with an average functionality between 4 and 6. These low molecular weight rubbers were used as a macro-initiator for the subsequent lactide/ glycolide polymerization. Star-shaped lactide/glycolide block copolymers with a poly[(trimethylene carbonate)co-(epsilon-caprolactone)] rubber core based on D-sorbitol show good mechanical properties. At relatively low rubber content ductile tensile behavior was observed indicating extensive toughening.

Flexible polyurethane foam wastes can be advantageously treated by two-phase glycolysis to recover the polyols with an improved quality compared to single-phase processes. This reaction has been traditionally catalyzed by alkanolamines, titanium compounds, or acetates. Recently, the employment of new catalysts based on potassium and calcium octoates has opened up a new way to catalyze the glycolysis of polyurethanes. In this work, the use of stannous octoate, which has never before been applied in the glycolysis reactions of polyurethanes, is proposed. The catalytic activity of stannous octoate in such a process was studied. The decomposition rate and the purity of polyol obtained were greater than those obtained using other catalysts previously employed for this application.

Blends of D,L-lactide/glycolide copolymers were synthesized and their properties and in vitro degradation behaviour were evaluated as a function of chain architecture and blend composition. Tensile and impact properties of the blends are hardly influenced by matrix composition and chain architecture, but predominantly vary with the amount of rubber. In vitro degradation showed that hydrolytic degradation is enhanced by the incorporation of glycolide into the poly(D,L-lactide) matrix. Surprisingly, blends based on 6-arm star-shaped poly(D,L-lactide-co-glycolide) retain their mechanical properties for a longer period than blends with linear matrices of comparable composition. Physical aging of the linear copolymers is more severe and faster than that of star-shaped copolymers. (C) 1997 Elsevier Science Ltd.

The ring-opening polymerization of lactide cyclic monomers in the bulk in the presence of tin(II) 2-ethylhexanoate (stannous octoate or SnOct2) was reexamined under conditions allowing for the end group characterization of growing chains by high-resolution 1H-NMR. Data collected for low values of the monomer/initiator (M/I) ratio showed that the DL-lactide ring was opened to yield lactyl octoate-terminated short chains. A cationic-type mechanism involving co-initiation by octanoic acid was proposed to account for experimental findings. The formation of a side product, hydroxytin(II) lactate (HTL), was found which appeared able to initiate lactide polymerization and to yield a high molecular weight PLA50 polymer. However the polymerization with stannous octoate was faster than the HTL one. Anyhow, data suggested that both SnOct2 and HTL are likely to act simultaneously as initiators during the polymerization of lactides in the presence of SnOct2. A complete reaction scheme was proposed to account for the presence of the various compounds likely to be formed under these conditions. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3431–3440, 1997

AB block copolymers of ε-caprolactone and (L)-lactide could be prepared by ring-opening polymerization in the melt at 110°C using stannous octoate as a catalyst and ethanol as an initiator provided ε-caprolactone was polymerized first. Ethanol initiated the polymerization of ε-caprolactone producing a polymer with ε-caprolactone derived hydroxyl end groups which after addition of L-lactide in the second step of the polymerization initiated the ring-opening copolymerization of L-lactide. The number-average molecular weights of the poly(ε-caprolactone) blocks varied fron 1.5 to 5.2 × 103, while those of the poly(L-lactide) blocks ranged from 17.4 to 49.7 × 103. The polydispersities of the block copolymers varied from 1.16 to 1.27. The number-average molecular weights of the polymers were controlled by the monomer/hydroxyl group ratio, and were independent on the monomer/ stannous octoate ratio within the range of experimental conditions studied. When L-lactide was polymerized first, followed by copolymerization of ε-caprolactone, random copolymers were obtained. The formation of random copolymers was attributed to the occurrence of transesterification reactions. These side reactions were caused by the ε-caprolactone derived hydroxyl end groups generated during the copolymerization of ε-caprolactone with prepolymers of L-lactide. The polymerization proceeds through an ester alcoholysis reaction mechanism, in which the stannous octoate activated ester groups of the monomers react with hydroxyl groups.

The synthesis of polylactide (PLA)-b-polyethylene glycol (PEG) linear block copolymers and their use in blends with pure-PLA is described. PLA-b-PEG linear block copolymers were obtained by the reaction between poly(ethylene glycol) bis (2-aminopropyl ether) (molecular weight 2000 Dalton) with PLA in the presence of stannous octoate via trans esterification. Molecular weight measurements of the block copolymers indicated that AB and ABA type block copolymers were obtained by controlling the feed ratio in the trans esterification reactions. The copolymers obtained were purified by the fractional precipitation and then characterized by 1H-NMR, FTIR, GPC and DSC techniques. Blends of pure PLA with PLA-b-PEG displayed improved mechanical properties compared to pure PLA. Thermal, mechanical and morphological characterization of the blends were also conducted. © 2012 Taylor and Francis Group, LLC., Fundamental Research Fund of Shandong University: 2011.10.03.01 108T423, This work was financially supported by TUBITAK (Grant #108T423) and Zonguldak Karaelmas University Research Fund (2011.10.03.01).

Several biodegradable polymers including polyglycolide (PGA), polylactide (PLA), and their copolymers are now widely used for biomedical applications in surgery, such as surgical suture, drug delivery systems, and internal bone fixation.

Linear and star-shaped copolymers of trimethylene carbonat/epsilon-caprolactone were synthesized using different polyol initiators and catalysts. Unexpectedly, when dipentaerythritol was used as an initiator cross-linked rubbers were obtained, that swell in chlorofonn. This network formation can be understood by 'in situ' generation of cross-linker molecules from trimethylene carbonate and initiator tor. SEC analysis showed that with D-sorbitol star-shaped copolymers are synthesized with an average functionality between 4 and 6. These low molecular weight rubbers were used as a macro-initiator for the subsequent lactide/ glycolide polymerization. Star-shaped lactide/glycolide block copolymers with a poly[(trimethylene carbonate)co-(epsilon-caprolactone)] rubber core based on D-sorbitol show good mechanical properties. At relatively low rubber content ductile tensile behavior was observed indicating extensive toughening.

An ABA block polymer, polyester-b-(aniline trimer)-b-polyester, was synthesized through the reaction of double amino-capped aniline trimer and 6-hexanolide, with stannous octoate as catalyst, via r...

Blends of D,L-lactide/glycolide copolymers were synthesized and their properties and in vitro degradation behaviour were evaluated as a function of chain architecture and blend composition. Tensile and impact properties of the blends are hardly influenced by matrix composition and chain architecture, but predominantly vary with the amount of rubber. In vitro degradation showed that hydrolytic degradation is enhanced by the incorporation of glycolide into the poly(D,L-lactide) matrix. Surprisingly, blends based on 6-arm star-shaped poly(D,L-lactide-co-glycolide) retain their mechanical properties for a longer period than blends with linear matrices of comparable composition. Physical aging of the linear copolymers is more severe and faster than that of star-shaped copolymers. (C) 1997 Elsevier Science Ltd.

AB block copolymers of e-caprolactone and (L)-lactide could be prepared by ring-opening polymerization in the melt at 110°C using stannous octoate as a catalyst and ethanol as an initiator provided e-caprolactone was polymerized first. Ethanol initiated the polymerization of e-caprolactone producing a polymer with e-caprolactone derived hydroxyl end groups which after addition of L-lactide in the second step of the polymerization initiated the ring-opening copolymerization of L-lactide. The number-average molecular weights of the poly(e-caprolactone) blocks varied from 1.5 to 5.2 × 103, while those of the poly(L-lactide) blocks ranged from 17.4 to 49.7 × 103. The polydispersities of the block copolymers varied from 1.16 to 1.27. The number-average molecular weights of the polymers were controlled by the monomer/hydroxyl group ratio, and were independent on the monomer/stannous octoate ratio within the range of experimental conditions studied. When L-lactide was polymerized first, followed by copolymerization of e-caprolactone, random copolymers were obtained. The formation of random copolymers was attributed to the occurrence of transesterification reactions. These side reactions were caused by the e-caprolactone derived hydroxyl end groups generated during the copolymerization of e-caprolactone with pre-polymers of L-lactide. The polymerization proceeds through an ester alcoholysis reaction mechanism, in which the stannous octoate activated ester groups of the monomers react with hydroxyl groups.

In the presence of stannous octoate, high molecular weight polydimethylsiloxane (PDMS) is obtained from an oligomeric α,ω-dihydroxy PDMS. The polycondensation reaction is limited by the presence of oxygen and/or water. Only linear species are found, and network formation has never been observed.

Since the rates of chemical reactions in volved in cellular urethane formation are decisive for product quality, model reactions were kinetically investigated and the mech anism of catalysis was studied. A simple rela tionship found between the specific rate con stant and the molar ratio of alcohol/catalyst for an alcohol/isocyanate reaction catalyzed by stannous octoate suggests the formation of an activated intermediate complex. The balance between the alcohol/isocyan ate and water/isocyanate reaction rates is important. Organotin compounds promote the former rate more than the latter whereas the reverse holds for amine catalysts. The rates of both reactions, catalyzed by amines with and without stannous octoate as co catal yst, demonstrate a synergistic effect ex plained by the extra stability imparted to the activated intermediate complex by attach ment of the amine.

This article describes preparation of resins as described in the title above, and the effect of concentration of the diepoxide, dimer acid, and initiator (stannous octoate). Proportion of dimer acid and diepoxide has a marked influence on hardness and tensile properties of resins. Change in tensile properties upon aging correlates very well with change in hardness. Higher proportions of dimer acid produce softer, more flexible resins. The resins have unique electrical properties at temperature up to 175°C, apparently because of the high proportion of hydrocarbon in the resin.

Several N-(substituted phenyl)carbamoyloxylalkyl-1,3-heterocycles of the structure 3 were prepared from their respective α-hydroxyalkyl-1,3-heterocyclic alcohols 1. Efficient syntheses of the prerequisite novel 1,3-heterocyclic alcohols, such as 2-(α-hydroxyalkyl)-2-oxazolines, −5,6-dihydro-1H-1,3-oxazines, −1,4,5,6-tetra-hydropyrimidines, -imidazolines, and 4,5,6,7-tetrahydro-1H-1,3-diazepines were developed. Stannous octoate was found to effectively catalyze the formation of the carbamate 3 from heterocyclic alcohol 1 and aryl-isocyanate 2.

THE MORE FAVORABLE RESULTS associated with early treatment of cancer foster continued effort to increase the accuracy and sensitivity of diagnostic methods. This motivation has led to modifying and improving radiologic and endoscopic techniques and to developing more precise means for collecting and studying exfoliative specimens of the colon. To this end we are attempting to improve the detection of tumors within the human sigmoid colon by evaluating a diagnostic enema that can be retrieved as a precise mold of the bowel to permit the recognition of small mucosal irregularities and the recovery of adherent cells. Method and Subjects The 125-ml enema is a nontoxic, liquid prepolymer of dimethylpolysiloxanes made radiopaque with barium sulfate or sodium diatrizoate. Polymerized by 2 ml of stannous octoate, the siliconeelastomer changes endothermically to a soft, elastic foam that molds the viscus containing it. The formulation and the techniques for administering the enema have been